Genesis 13:18 and Genesis 18:1

trees (terebinths, plains, oaks) of Mamre

13:18 Then Abram moved his tent and came and dwelt among the terebinths (oak trees) of Mamre, which are in Hebron, and built there  an altar to the Lord.

18:1 Now the Lord appeared to Abraham by the trees (terebinths, plains, oaks) of Mamre, as he sat….

the word trees(terebinths, plains, oaks) gives a list of Hebrew word definition:

ram, sacrifice, doorpost, pillar

the word Mamre Hebrew definition is: strength

Abraham built an altar to the Lord while dwelling in the trees of Mamre. 

“a sacrifice of strength”

In our weakness He is strong

Abraham was barren (Sarah)

Isaiah 54:1 

Sing oh barren one

We bring a sacrifice of praise (song).. Psalm 49

In Genesis 12 Abram had just been told to leave all he knew and go to a land the Lord had for Him.

The Lord appeared to Abraham in 18:1 after his name was changed by the Lord and he was about to be told Sarah would have his son.

Here is a picture of tree of Mamre where Abraham pitched his tent, met with the Lord, and entertained the three angels from Genesis chapter 18